Support is requested for a Keystone Symposia meeting entitled T Follicular Helper Cells and Germinal Centers, organized by Shane Crotty and Carola G. Vinuesa. The meeting will be held in Monterey, California from February 26 - March 1, 2016. Follicular helper CD4 T cells (Tfh) are the specialized providers of B cell help and are essential for germinal center function and most antibody responses. It is well established that germinal centers are the engines of rapid B cell evolution and have exquisitely complex cellular dynamics. But it has only recently emerged that Tfh are major players in protective immunity to pathogens, generation of high affinity and long term antibody responses to vaccines, autoimmune diseases, allergies, and even cancer. Critically, there are major gaps in our understanding of Tfh function, germinal center function, and the biological selection of high affinity antibodies responses in vivo in a variety of relevant anti-pathogen and autoimmune contexts. Furthermore, it is apparent that the differentiation of Tfh is a multistage, multifactoril process, but the specific details of these processes are only now being uncovered. This Keystone Symposia meeting will bring together scientists and physicians from a range of disciplines and disease models to elaborate the complex biology of Tfh cells and germinal centers and discuss emerging avenues to manipulate them in clinical settings.